In the metalworking art, it is known to employ metal-cutting tools which utilize round cutting blades or cutting wheels, each such blade or wheel having a sharpened cutting edge ground about its outer periphery. The blades are generally arranged in pairs to position the cutting edges proximate one another and to slightly overlap the cutting edges thereof. The sheet material to be cut is passed between the cutting edges, which "engage" the material and sever it. Due to the relative thinness of the cutting edges, the pressure with which the sheet material engages the cutting blades creates force sufficient to easily sever or shear the sheet material. Unlike other metal cutters, such as rotary nibblers, which create ribbons of waste or scrap material when used, the rotary shear cutters with which the present invention is involved generally create no such waste or scrap, making neat, accurate cutting more possible. While such cutting blades or wheels are generally arranged in opposed pairs, they may take on other configurations as well.
The present invention concerns itself with the type of shear cutter that is generally characterized as portable and hand-operable, rather than those types of cutters utilizing motor-driven blades, or that type of cutting machinery housed in large, permanently-positioned cabinets where the stock to be shaped is brought to the machine rather than vice versa. A preferred and intended manner of use for the present invention contemplates laying the sheet stock on a supporting surface, positioning the cutter at the farthest edge of the sheet stock, and drawing the cutter toward the user, shearing the sheet stock as the cutter travels.
Known cutters employing these mechanical principles have suffered from various shortcomings which limit their usefulness and increase their operating expense. Among these shortcomings is the expense and inconvenience suffered when the cutter is manufactured as a unitary structure, making it difficult and expensive, or even impossible to repair. If the handle breaks, the cutter may have to be discarded or may have to be welded or otherwise patched back together in a temporized form of repair. Another problem is incurred when the length and/or shape of the handle makes it inconvenient or awkward to use the cutter for a particular application. One solution to such problems is to keep a stock of cutters on hand having handles of varied lengths and shapes, a solution which also calls for a higher capital outlay.
Prior cutters illustrated in issued U.S. Patents demonstrate these shortcomings. U.S. Pat. No. 4,283,853, issued Aug. 18, 1981, shows a unitary cutting head frame and handle construction to which the cutting wheels are attached, with no provision for varying the distance between its cutting head frame and the handle. U.S. Pat. No. 769,081, issued Aug. 30, 1904 also shows a cutter with a unitary cutting head and handle structure to which the cutting wheels are affixed.
Similar constructions are shown in U.S. Pat. No. 1,511,892, issued Oct. 14, 1924, and U.S. Pat. No. 2,276,365, issued Mar. 17, 1942. The unitary attachment shown in these patents is self-limiting in the manner described hereinabove.